feat: move kubernetes dir into templates to support jinja2 across all files (#831)

template/templates/kubernetes/apps/default/echo-server/ks.yaml.j2

@@ -0,0 +1,16 @@
+---
+apiVersion: kustomize.toolkit.fluxcd.io/v1
+kind: Kustomization
+metadata:
+  name: cluster-apps-echo-server
+  namespace: flux-system
+spec:
+  path: ./kubernetes/apps/default/echo-server/app
+  prune: true
+  sourceRef:
+    kind: GitRepository
+    name: home-kubernetes
+  wait: false # no flux ks dependents
+  interval: 30m
+  retryInterval: 1m
+  timeout: 5m